Note: Descriptions are shown in the official language in which they were submitted.
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WAST~ TR~AT~E~T SYST~l HAVI~G
INTEGRAL I~TRA_H~ L C],ARIFI~
SUMMARY OF THE iNVENTION
The present invention relates generally to a waste
water treatment system, and more particularly to aerobic
waste water treatment systems of the type using an oxida-
tion ditch system including an intrachannel clarifier ?osi-
tioned within the oxidation ditch channel.
Generally, waste treatment systems may be divided into
two types of broad categories. The first category involves
waste waters containing organic and inorganic dissolvet and
suspended solids which are amenable to chemical treatment
and subsequent clarification, as by oxidation, reduction,
neutralization, and the like. A sludge is usually formed
which is separated by holding under quiescent conditions, r
usually for a considerable length of time, in a settling
tank, where the inorganic solids settle by gravity to the
bottom of the tank. The settled sludge must be removed by
mechanical means, and the remaining waste liquor may
require chemical neutralization for disposal. The sludge
material may be disposed of in a number of different ways
as is well known in the art. The waste water may be re-
cycled or discharged to a public waterway. A common source
of such waste liquids are pickle acids or pickling rinse
waters resulting from steel plant operations.
The present invention is concerned with the general
broad category of waste materials which contain biodegrad-
able solids. Such waste liquids may result from municipal
sewage collection systems, oil refineries, coke plants,
paper making plants, canneries, food processing plants
and the like. The treatment of these organic dissolved
and suspended materials is normally accomplished by aerobic
processes commonly classified as biological treatment.
Removal of the organic material by these processes is
3~ accomplished by two general mechanisms. First, impurities
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are adsorbed and absorbed at the interface between the
associated biomass and waste liquid. Second, the biomass
decomposes these organics through oxidation, thus synthe-
sizing new cells and releasing gases such as carbon
dioxide. The resulting increased biomass or sl~dge con-
sisting of accumulated micro-organisms is ~enerally sep-
arated from the organically stablized liquid. ~hile
most of the biomass is generally returned to the process
to continue the process, excess sludges are normal.ly wasted
from the system.
In conventional aerobic treatment systems, the major
components are frequently an aeration tank and a clarifier.
In one type of treatment system, the aeration tank is
rectangular or circular, andincludes means for continually
circulating the waste liquid within the tank with the addi-
tion of oxygen or air to promote micro-organism growth.
In a second type of aeration tank, the tank is generally
oval in shape and defines a trough-like channel having a
bottom and spaced upstanding sidewalls for retaining the
waste liquid in a continuous substantially closed flow
~ path. In this type of system, which is often referred to
as an oxidation ditch, the waste liquid is continuously
circulated by means of rotating brushes, discs, turbines
or the like, at a flow velocity sufficient to maintain the
~ 25 solids in suspension. Additional air or oxygen may also
be added to the circulating waste liquid to promote micro-
organism growth.
Both types of systems require a clarifier for sep-
arating suspended solids from the waste liquid, commonly
referred to as mixed liquor, and disposing of the clarified
liquid. In conventional oxidation ditch systems, the clar-
ifier comprises a separate unit frequently located adjacent
an outside edge of the aeration channel, which forms
a settling tank for separating suspended solids from the
waste liquid. The clarified liquid may be disposed of or
reused, while the settled biomass remains in the clarifier,
where it may be disposed of as waste sludge, or recycled
to the oxidation ditch to maintain the proper balance
,
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between organic loading and biological microbial mass
solids in the mixed liquor.
Periodically, the settled sludge in the clarifier must
be removed by mechanical means such as scrapers, pum?s or
the like. As noted, a portion of the sludge may be re-
turned to the oxidation ditch for further digestion. In
any event, it has been found that the use of such a
separate clarifier tank not only requires significant
installation and material costs together with land space
for the clarifier installation, but also a significant
expenditure of energy resources to remove the settled
sludge from the clarifier, as well as to move the sludge
between the oxidation ditch and the clarifier.
The present invention significantly reduces equipment
and energy requirements associated with aerobic waste
treatment facilities of the type described by incorporating
the clarifier within the oxidation ditch flow channel.
While for purposes of an exemplary showing, the intra-
channel clarifier of the present invention has been
described and illustrated in colmection with an oxidation
~ ditch treatment system, it will be understood the inven-
tive principles may be extended to other aeration tank
configurations. In the embodiment described, the intra-
channel clarifier is positioned downstream from the aeration
means or means for imparting a flow velocity to the liquid.
A portion of the mixed liquor being circulated in the
oxidation ditch is allowed to pass into the clarifier zone.
Once within the quiescent zone established inside the
clarifier, suspended solids settle by gravity to a
specially constructed clarifier bottom. Consequently,
liquid-solid separation occurs as it would in a conventional
rectangular sedimentation basin with the clarified super-
natant being discharged over an effluent weir. The
majority of the mixed liquor being circulated in the oxi-
dation ditch does not enter the quiescent clarification
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1 zone, but ra-ther passes beneath it at sufficient velocity
to maintain solids in suspension. As the mixed liquor
passes beneath the clarifier, sludge is hydraulically
drawn from the clariEier bottom and resuspended in the
mixed liquid. Sludge is wasted from the system by
wasting a stream of mixed liquor.
According to the invention there is provided an
intrachannel clariier for clarifying waste liquid con-
taining settlable solids for use in an aerobic wastewater
treatment system of the type having means for retaining
the waste liquid in continuous substantially closed flow
path, means for introducing wastewater influent into the
flow path, means for removing waste sludge as mixed
liquor from the flow path, and means for moving the waste
liquor in a single direction in the flow path at suffi-
cient velocity to prevent settling of the suspended
solids, said clarifier comprising: tank means posi-
tionable within said retaining means for creating a zone
of relatively quiescent waste liquid in the upper portion
of the tank means to permit suspended solids to settle
downwardly by gravity within the quiescent zone to pro-
duce clarified waste liquid; clarifier inlet means
included in said tank means to permit entry of uncla-
rified mixed liquor from the flow path into the quiescent
zone at a relatively slow rate; and baffle means associ-
ated with said tank means for permitting the settled
solids to return from the quiescent zone to the flowing
mixed liquor within the retaining means but preventing
movement of excessive quantities of flowing mixed liquor
into the quiescent zone, said baffle means comprising a
plurality of spaced parallel slightly overlapping
inverted V-shaped angle members configured to extend
across the retaining means transversely of the waste
liquid flow direction each of said angle members having a
pair of angularly disposed legs configured to lie across
` !
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1 the :Elow path when the clarifier i9 positioned within the
retaining means, adjacent legs of adjoining angle members
being spaced to permit the passage of settled solids
therebetween, said angle members being configured such
that settling of suspended solids occurs in the quiescent
zone above said baffle means.
Preferably the downstream leg of each angle member
is longer in the flow direction than the upstream leg.
The angle members are preferably disposed within the tank
such that the upper surfaces of the legs are inclined at
angles of approximately 30~-60 with respect to the
horizontal to prevent collection of settled solids on the
angle members. It is believed that the angle members
tend to create a draft for hydraulically drawing settled
solids from the clarifier tank into the waste liquid
underflow.
In one embodiment, the intrachannel clarifier is
constructed in the form of a tank of similar construction
to that described hereinabove positionable within an
existing oxidation ditch channel, thereby permitting
retrofitting of established waste treatment systems. In
this embodiment, the tank is constructed to be positioned
at approximately mid-depth within the oxidation ditch
channel thereby permitting underflow of the flowing mixed
liquor to draw settled solids through the slatted tank
bottom.
In all embodiments, sludge is wasted from the system
by wasting a stream of mixed liquor at a location
downstream from the intrachannel clarifier.
Further features of the invention will become
apparent from the detailed description which follows:
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a partially schematic top plan view of a
typical oxidation ditch waste treatment system incorporating
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the intrachannel clarifier of the present invention.
Fig. 2 is a fragmentary cross sectional view taken
along section line 2-2 of Fig. l.
Fig. 3 is a fragmentary cross sectional view taken
along section line 3-3 of Fig. 1.
Fig. 4 is a fragmentary perspective view of the
intrachannel clarifier of the present invention.
Fig. 5 is a fragmentary top plan view of a second
embodiment of the intrachannel clarifier of the present
invention.
Fig. 6 is a fragmentary cross sectional view taken
along section line 6-6 of Fig. S.
Fig. 7 is a fragmentary cross sectional view taken
along section line 7-7 of Fig. 5.
Fig. 8 is a fragmentary cross sectional end view of
a third embodiment of the intrachannel clarifier of the
present invention.
DETAIL~3 DESCRIPTIOi~
An oxidation ditch waste treatment system, shown
~enerally at l, incorporating a pair of intrachannel
clarifiers of the present invention, shown generally at
2, is illustrated in Fig. 1. '~hile for purposes of an
exemplary showing, the intrachannel clarifier is described
and illustrated in connection with an oxidation ditch
type of waste treatment system, it will be understood
that the inventive principles of the present invention
may be applied to any type of waste treatment system where
the waste liquid is treated in an aeration tank configur-
ation. The waste treatment system 1 illustrated in Fig. 1
comprises an oval or race track-shaped oxidation ditch 3
defining a trough-like channel 4 havin~ a bottom 5 and
spaced upstanding side walls 6 and 7 for retaining the
waste liquid in a continuous substantially closed flow
path. Channel walls 6 and 7 may be positioned vertically,
or slanted outwardly as illustrated in Fig. 2 such that
the flow channel is wider at the top than at the bottom.
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Oxidation ditch 3 may be constructed from any suitable
material such as earth, concrete, fiberglass, steel or the
like, and may be embedded in the ground to facilitate con- -
struction of the channel. Means are provided in the form
of a pipe or conduit 8 for introducing waste water influent
into the oxidation ditch flow path. In the embodiment
illustrated, inlet conduit ~ is positioned near the end of
oxidation ditch 3, downstream from intrachannel clarifier
2. Similarly, means in the form of an outlet conduit 9
are provided for removing waste sludge from the flow path
by wasting a stream of mi~ed liquor. In the embodiment
illustrated, outlet conduit 9 is positioned on the outer
edge of oxidation ditch 3 between inlet conduit 8 and
intrachannel clarifier 2. However, it will be understood
that both the inlet and outlet conduits may be positioned
at other locations on the oxidation ditch as required.
Means 10 are provided for aerating and moving the
waste liquid in a single substantially horizontal direction
in the flow path as indicated by directional arrows 11
at sufficient velocity to prevent settling of the suspended
~ solids; As illustrated in Fig. 1, moving means 10 are pro-
vided spaced from the upstream edge of each intrachannel
clarifier 2. In general, for waste liquid resulting from
municipal sewage operations and the like, the flow velocity
provided by moving means 10 will be approximately one foot
per second in order to maintain adequate solid suspension.
In any event, it is preferred that moving means 10 be suf-
ficiently spaced from intrachannel clarifier 2 to prevent
agitation of the settling solids in the quiescent zone of
the clarifi~er as will be described in more detail herein-
after.
Moving means 10 may comprise any one of a num~er of
different types of aerators or pumping mechanisms. For
example, the moving means may be implemented by a plurality
of brush-like bristles or slotted discs attached to a
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slowly rotating horizontal shaft extending transversely of
the oxidation ditch channel in contact with the waste
liquid, which agitates and aerates the waste liquid, and
at the same time imparts a velocity vector to create uni-
directional flow. Alternatively, the moving means maycomprise a turbine for creating waste liquid flow and
aerating the liquid to enhance the growth of micro-
organisms. The moving means may also be implemented by
means of ejectors directed in the direction of desired
flow for aerating and agitating the waste li~uid.
The oxidation ditch waste treatment system described
hereinabove is essentially conventional in nature, and well
understood by those skilled in the art. However, as noted
hereinabove, such systems generally require the use of a
separate clarifier for separating solids from the mixed
liquor. To eliminate the problems associated with such
separate settling or clarifying tanks, the present inven-
tion utilizes an intrachannel clarifier 2 positioned within
the flow channel of the oxidation ditch. While the embodi-
ment of the invention illustrated in Fig. l-Fig. 4 utilizes
two intrachannel clarifiers positioned within the oxida-
tion ditch, it will be understood that the system may be
operated with but one intrachannel clarifier, such as that
illustrated in connection with the cross sectional views
illustrated in Fig. 2 and Fig. 3. Likewise, it will be
understood that the system may be operated with more than
two intrachannel clarifiers.
In the embodiment of Fig. l-Fig. 3, intrachannel
clarifier 2 comprises tank means 12 for creating a zone
13 (see Fig. 3) of relatively quiescent waste li~uid in
the upper portion of channel 4 to permit sus?ended solids
to settle downwardly by gravity within the quiescent zone
to produce clarified waste liquid. It will be understood
that tank means 12 may be constructed as an integral part
of the oxidation ditch channel, or provided as a separate
I 160767
unit t.o retrofit existing waste treatment facilities as
will be described in more detail hereinafter.
Tank means 12 includes a vertically positioned
` upstream wall 14 extending completely across the flow
path within channel 4 to a depth of approximately one-half
to three-quarters of the channel depth. Wall 14 may be
constructed of concrete, steel, fiberglass or the like, and
may be formed as an integral part of the channel as
illustrated in the embodiment of Fig. l-Fig. 4, or may be
bolted or otherwise secured to the inner surfaces of channel
walls 6 and 7, respectively. It will be understood that
wall 14 need not extend completely across the flow path,
but that additional side walls would be required in that
case as will be explained more fully hereinafter.
Upstream wall 14 contains a generally rectangular
central opening 15 extending through the wall permitting
entry of unclarified waste liquid from the flow path into
quiescent zone 13 at a relatively slow rate. It will be
observed that upstream wall 14 and associated opening 15
~ 20 cause the majority of the waste liquid to flow beneath the
lowermost edge of wall 14 as illustrated by flow path
arrow 16 to form the intrachannel clarifier underflow 17.
In general, clarifier inlet 15 will be positioned below
the upper surface 18 of the waste liquid. As will be
explained in more detail hereinafter, in some situations
it may be desirable to eliminate opening 15, such that
unclarified waste liquid enters the quiescent zone throu~h
the perforated or slotted floor of the clarifier.
In the embodiment illustrated the terminal end of
clarifier 2 is formed by a vertically positioned wall 19,
similar in construction and shape to upstr~am wall 14,
spaced downstream from the upstream wall, and extending
completely across the flow path within channel 4. In
general, the lower edges of walls 14 and 19 will extend
to approximately the same depth within channel 4. It will
l 160767
be observed that this arrangement restricts the ~ajority
of waste liquid flow to the region beneath clarifier 2.
It is believed that liquid flow in the underflow area 17
will generally be turbulant in nature. In any event,
it will be desirable to maintain the flow velocity at a
sufficient level to insure suspension of solids in the
underflow area to prevent accumulation oE sludge on the
upper surface of channel bottom 5 in the underflow area.
~For liquid waste associated with municipal sewage facili- _
ties, it is believed that a flow velocity in the underflow
area of no less than one foot per second should be suffi-
cient to maintain solid suspensions. However, the actual
flow velocity may depend somewhat on the particular type
of liquid being treated, and the nature of the suspended
solids.
As best shown in Fig. 3, the channel bottom 5 in the
region of the underflow area may be deevened as at 20 to
facilitate waste liquid flow. This deepened portion insures
that the flow velocity of the liquid waste is not affected
to any appreciable extent by the restrictions presented by
~ walls 15 and 19.
Deepened portion 20 may also be utilized to affect
the hydraulic performance of the clarifier bottom as will
be described in more detail hereinafter.
In order to remove clarified liquid, clarifier 2 is
provided with clarifier outlet means 21 comprising a trough-
like overflow weir or launder positioned within the clari-
fier and extending between channel walls 6 and 7. As best
shown in Fig. 3, the upper edges 21a of clarifier outlet
means 21 are positioned sli~htly below the upper surface
level 18 of the waste liquid, so that the weir removes a
portion of the supernatent. Weir 21 extends through channel
wall 7 as at 22, to conduct the clarified liquid to a
suitable disposal site (not shown). ~hile an overflow weir
or launder has been illustrated as the clarifier outlet
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11
means for purposes of an exemplary showing, it will be
understood t'lat other types of apparatus may be utilized
for removing the clarified liquid from within clarifier 2.
The floor or bottom of clarifier 2 comprises baffle
means, shown generally at 23, for permitting the settled
solids to return from quiescent zone 13 to the flowing
mixed liquor within underflow area 17, bl~t preventing
movement of excessive quantities of flowing mixed liquor
into the quiescent zone. In a preferred embodiment, the
baffle means forms a perforated or slotted bottom compris-
ing a plurality of spaced parallel slightly overlapping
inverted V-shaped angle members, one of which is snown at
24, having angularly disposed upstream and downstream legs
25 and 26, respectively. Angle members 24 extend between
channel walls 6 and 7 in spaced parallel relationship with
channel bottom 5, and may be integrally cast with the
channel walls as illustrated in Fig. 2, or attached to the
inner surfaces of the walls by any convenient means. Alter-
natively, slots may be provided in theinner surfaces of
the channel walls for supporting the ends of the angle
members in the proper orientation. ~s best shown in Fig.
3, the upstream leg 25 of the adjacent angle member 24
overlaps the upper surface of plate member 23a.
It will be observed that this arrangement forms a
plurality of spaced sloping surfaces extending across the
flow path. In general, angle members 24 may be constructed
of steel, fiberglass or other material having generally
smooth surfaces permitting settled solids to slide easily
downwardly along the sloping surfaces into the underflow
region. In some instances, the angle members may be re-
placed by a purality of parallel spaced slanted plates
extending between and supported by the channel walls.
In either event, the baffle means acts as a baffle to
preclude interruption of the quiescent zone by waste liquid
flowing in the underflow area by diverting water away froln
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.
12
the openings 24a between the haffle surfaces. In ad~ition,
it is believed the sloped surfaces form a draft caused by
the flowing mixed liquor in t'ne underflow area tending to
suck or draw the settled slud~e from the quiescent zone
as indicated by direction~l arrows 24b in Fig. 3.
To obtain these objectives, the downstream leg 26 of
each angle member is longer in the flow direction than the
upstream leg 25, the lep~s being angularly disposed with
respect to each other. Adjacent legs of ~djoining an~le
members are also angularly disposed and sp~ced to ?ermit
the passage of settled solids in the space between the
adjacent leg members. As best shown in Fig. 3, the up-
stream leg overlaps the downstream leg of an adjoining
angle member. In the preferred embodiment illustrated,
the an~le members are disposed such that the upper
surfaces of the upstream and downstream legs are inclined
at angles of approximately 30-60 with respect to the
waste liquid flow to prevent collection of settled solids
on the surfaces of the angle members. It is also believed
that this angular orientation is necessary to create a
~ draft for drawing settled solids from the clarifier into
the underflow area, much in the manner of an aspirator.
To insure a substantially continuous bottom forming
baffle means 23, a baffle plate member 23a extending down-
wardly at an angle of 30-60 may be provided at the lower
edge of upstream wall 25. In general, plate me~ber 23a
will be similar in construction and orientation to down-
stream legs 26 of angle members 24.
It will be observed that this arrangement of the
baffle means 23 permits settling of the suspended solids
to the clarifier bottom by ~ravity. The sloping surfaces
in the bottom prevent deposition of the settled solids on
these surfaces, as well as serving to channel the sludge
to the open root of the multiple V configurations formed
by adjacent angle members. As the mixed liquor passes
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under the clarifier, it is believed that sludge i.s hydxaulically drawn from the
V-shaped bottoms and resuspended in the mixed liquor passing under -the clarifier.
It will be understood that various changes in the details, materials,
steps and arrangements of parts, which have been herein described and illustrated
in order to explain the nature of the invention, may be made by those skilled in
the art within theprinciple and scope of the appended claims. For example, it
may be desirable in some installations to eliminate or severely res-trict the
si~e of the opening forming clarifier inlet 15 in upstream wall 14. In this
configuration, a portion of the mixed liquor bearing settlable solids flowing in
the underflow area 17 passes through the slots or spaces 24a between adjacent
angle members 24 into quiescent zone 13. Since the flow velocity within the
quiescent zone is insufficient to maintain solid suspensions, the solids
settle from the mixed liquor and move downwardly into the underflow liquid.
The clarified liquid is then removed by means of the overflow weir forming
clarifier outlet means 21 in the manner described hereinabove.
Similarly, downstream wall 19 can be eliminated in some situations
provided the flow velocity within quiescent zone 13 is less than that
necessary to suspend settlable solids. In this modification, it may be
necessary to restrict the size of the opening forming clari~ier inlet
15 in order to restrict the waste liquid flow veloci~y below the critical
value necessary to suspend settlable solids. In all other respects,
operation of clarifier 2 is identical to that described hereinabove.
Operation of the clarifier may also be affected by modification
of the channel bottom in the area adjacent the clarifier underflow. As
described hereinabove, the
- 13 -
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14
channel is provided wi.th a dee~ened cl~annel area 20 to
prevent restriction of the waste liquid flow and possible
reduction in the flow velocity which mi~ht cause settlable
solids to accummulate as sludge on the floor of the channel
in the underflow area. However, in some situations it may
be desirable to slightly restrict the flow velocity, there-
by causing` a head loss between the upstream and downstream
boundries of the baffle means 23 to assist in drawing
settled solids from the quiescent zone. However, in this
situation, the decrease in cross sectional area of the
underflow will be insufficient to cause the velocity to
fall below a level capable of maintaining settlable solids
in suspension.
As an alternative to providin~ a deepened channel
area 20 in the underflow region, the entire oxidation ditch
channel could be widened in the region of clarifier 2 in
order to increase the cross sectional area of the underflow
thereby maintaining the flow velocity substantially constant.
This alternative may be advantageous when the nature of
the settlable solids is such that excessive sludge could
~ tend to accumulate in the deepened channel area 20 in the
configuration illustrated in Fig. 3, for example, or where
extensive clarifier surface area is required.
Another embodiment of the present invention is illus-
trated in Fig. 5-Fig. 7, where elements similar to those
described hereinbefore in connection with the embodiment
of Fig. l-Fig. 3 have been given similar reference desig-
nations.
This embodiment illustrates an intrachannel clari-
fier 27 constructed as a separate unit which can be addedto existing oxidation ditch waste treatment systems.
Fundamentally, clarifier 27 is sirnilar in construction and
operation to intrachannel clarifier 2 described herein-
before, and comprises tank means 2~ positionable within
oxidation ditch channel 4 for creating a zone of relatively
quiescent waste liquid 13 in the upper portion of the
channel to permit suspended solids to settle downwardly by
gravity within the quiescent zone to produce clarified
1 1~0767
waste liquid. Tank means 2~ includes a vertically posi-
tioned upstream wall 14 con~igured to extend conpletely
across the flow pa~.h within channel 4 when clarifier
27 is in place. An opening 15 formino a clarifier i.nlet
extends through wall 15 to permit entry of unclarified
waste liquid from the flow path into quiescent zone 13 at
a relatively slow rate. As described hereinabove, opening
15 may be eliminated in certain designs. Furthermore,
tank means 28 may be dimensioned to extend only partially
across the flow path within channel 4.
A vertically positioned wall 19 is spaced downstream
from upstream wall 14, and is also configured to extend
across the flow path within channel 4 when the clarifier
is in place. Both walls are vertically dimensioned to
permit waste liquid flow between the lower edges of the
wall and the channel bottom 5. As noted above, downstream
wall 19 may also be eliminated for particular design con-
figurations.
Baffle means 23 forming the bottom of tank means 23
permit the settled solids to return from quiescent zone 13
to the waste liquid underflow, but prevent infiltration to
any great degree of flowing waste liquid into the quiescent
zone. As described hereinabove, baffle means 23 comprises
a plurality of spaced parallel slightly overlapping inverted
V-shaped angle members, one of which is shown at 24, having
a pair of angularly arranged upstream and downstream
legs, 25 and 26. The angle members 24 are arranged in
spaced parallel relationship with the channel bottom S
when clarifier 27 is positioned within the channel. As
noted above, the downstream leg 26 of each angle member
24 is longer in the flow direction than and angularly dis-
posed with respect to upstream leg 25, adjacent legs of
a~joining angle members bein8 angularly disposed and spaced
as at 24a to permit the passage of settled solids there-
between. The angle members are generally disposed such that
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1~
the upper surfaces of each leg are inclinecl at a,lgles of
approximately 30-60 with respect to the horizontal to pre-
vent collection of settled solids. I~owever, as noted above,
the particular orientation of the angle member le~ surfaces
will depend somewhat upon the particular type of solids
suspended in the mixed liquor, particularly, the angle of
repose of the solids, etc. In any event, it is believed
that the angle members tend to create a draft for drawing
solids from the clarifier means 27 when the tank means is
positioned within channel 4. To insure a substantially
continuous bottom forming baffle means 23, a baffle plate
member 23a extending downwardly at an angle of 30-60 may
be provided at the lower edge of upstream wall 25. In
general, plate member 23a will be constructed and oriented
as described hereinabove with respect to the embodiment of
Fig. l-Fig. 3.
In order to form tank means 28 as an inte~ral unit
which can be added to existing oxidation ditch waste treat-
ment systems to provide retrofit clarifying capability,
means 29 are provided for structurally connecting upstream
and downstream end walls 14 and 19, respectively, with
baffle means 23. In a preferred embodiment, connecting
means 29 comprises generally vertical spaced inner and
outer side walls 30 and 31, respectively. Side walls 30
and 31 extend between and are attached to the vertical
edges of upstream and downstream walls 14 and l9 in order
to form a generally rectangular box-like tank. The side
and end walls may be separately fabricated and attached by
any convenient means, or molded or cast in one piece.
This latter mode of construction is particularly advantage-
ous when tank means 28 is constructed from concrete, fiber-
glass or the like.
The inner and outer edges of angle members 24 are
secured to the inner surfaces of side walls 30 and 31 as
at 32 as shown in Fi~g. 6 by any convenient means. Alterna-
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tively, angle members 24 may be cast or molded as an integral part of theside and end walls, or may rest in grooves or slots provided in the inner
surfaces of the side walls. For example, tank means 28 may be constructed
entirely of concrete or fiberglass, for example, in one continuous casting
operation to include baffle means 23 forming the floor of the box-like tank.
In a similar manner, clarifier outlet means 21 in the form of a
channel-like weir or launder may be positioned within the tank means for
removing a portion of the clarified mixed liquor in a manner similar to that
described hereinbefore with respect to the embodiment of Figure 1 - Figure 3.
In the present embodiment, the outer end 22 of clarifier outlet means 21
extends through outer s-ide wall 31. In addition, a cut or opening 33 may
be provided in the outer-most channel wall 7 of oxidation ditch 3 to
accomodate the extension 22 of the clarifier outlet means. It will be under-
stood that the weir or launder may be provided as a separate assembly attached
by means not shown to tank means 28, or may be cast or molded as an integral
part of the box-like tank.
As best shown in Figure 6, side walls 30 and 31 taper inwardly
and downwardly to conform to the shape of channel walls 6 and 7, respectively.
In such a configuration where the oxidation ditch channel cross section is
trapezoidal-shaped, the intrachannel clarifier 27 will remain positioned in
and supported by channel 4 as illustrated in Figure 6 by its own weight without
additional attaching means. In situations where the channel walls are more
nearly vertical, or of other shapes, additional fastening means such as bolts
or the like may be necessary to hold clarifier 27 in place within the channel
to insure that baffle means 23 is positioned at the proper distance above channel
bottom S. It will be further understood that the channel bottom may be deepened
as illustrated at 20 in Figure 3 in the area of the clarifier to facilitate
removal of settled solids fromwithin quiescent zone 13.
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. .
18
It will be further understood that baffle means ~3
may be connected to either or both of u~stream end wall 14
or downstream wall 19 by other means. For example, the
side walls 30 and 31 may be elimin~ted entirely, and the
individual angle members 24 attached to ~ach other by
suitable means to maintain spaces 24a between the angle me~-
bers, with the endmost angle members being attached to
the adjacent end walls. This arrangement would ~esult in a
construction somewhat like that shown in Fig. 4, with the
clarifier comprising a U-shaped integral one piece unit
which can be positioned in an existing oxidation ditch to
provide retrofit clarifier capability. It will be further
understood that walls 30 and 31 may be replaced by plates,
straps, braces or the like connecting the ends of angle
members 24 with upstream and downstream walls 14 and 19.
As discussed hereinabove, the intrachannel clarifier
of the present invention may be constructed as at 2 where
chann~l walls 6 and 7 form the side walls of the clarifier
or in the form shown at 27 where outer side walls 30 and 31
define the side walls of the tank-like clarifier. In this
~ latter embodiment, the width of tank means 25 may be dimen-
sioned as required so that the clarifier extends partially
or completely across the flow path within channel 4 of the
oxidation ditch.
Alternatively, the intrachannel clarifier may be con-
structed as illustrated in Fig. ~. In this arrangement,
where elements similar to those illustrated in connection
with the embodiment of Fig. 5-Fig. 7 have been similarly
designated, inner side wall 30 has been eliminated and the
inner edges of end walls 14 and 15 secured directly to
inner channel side wall 6. The remainder of tank means 23
is identical to that described hereinabove except that the
width of the clarifier has been dimensioned so that outer
clarifier wall 14 is spaced inwardly of outer channel wall
31, permitting the clarifier to extend only partially across
1 160767
19
the channel flow path. Alternatively, the width of tank
means 28 may be adjusted so that the ciarifier exte~ds
completely across the flow path in a manner similar to the
arrangement of Fig. 5-Fig. 7.
